The technical field of this invention is phototherapy and, in particular, methods and devices which employ optical fibers and flexible light-waveguides to deliver radiation to a targeted site.
Destruction of cellular tissues in situ has been used in the treatment of diseases and medical conditions alone or as an adjunct to surgical removal procedures. These methods are often less traumatic than surgical procedures and may be the only alternative where surgical procedures are unfeasible. Phototherapeutic treatment devices, e.g., lasers, have the advantage of using intense light energy which is rapidly attenuated to a non-destructive level outside of the target region. However, blood and/or other body fluids greatly diminish the effectiveness of several of these light energy sources as the radiation passes from an energy source, e.g., a laser source, through the body fluid to a treatment site. For example, the energy can be scattered or be absorbed by blood and other body fluids between the energy source and the tissue treatment site.
A common medical application of lasers is in the irradiation of tissue, both internal and external. For external treatment, the laser energy can be applied directly. However, where a procedure requires irradiation of internal tissues that are not readily accessible to external energy sources, the use of catheter-type devices to deliver coherent radiation to the treatment site is common. Typical applications requiring use of laser catheters are found in the treatment of various anatomical structures and conditions within the cardiovascular system.
Microwave, radio frequency, and acoustical (ultrasound) devices as well tissue destructive substances have also been used to destroy malignant, benign and other types of aberrant cells in tissues from a wide variety of anatomical sites and organs. Tissues sought to be treated include isolated carcinoma masses and, more specifically, organs such as the prostate, bronchial passage ways, passage ways to the bladder, passage ways to the urethra, and various passage ways into the thoracic area, e.g., the heart.
Devices useful for the treatment of such disease states or conditions typically include a catheter or an cannula which can be used to carry an energy source or waveguide through a lumen to the zone of treatment. The energy is then emitted from the catheter into the surrounding tissue thereby destroying the diseased tissue, and sometimes surrounding tissue.
Catheters have been utilized in the medical industry for many years. One of the greatest challenges in using a catheter is controlling the position and placement of the distal portion of the catheter from a remote location outside of the subject""s body. Some catheters have features designed to aid in steering the catheter and overcoming this challenge. However, several significant problems are still encountered with catheters.
Careful and precise control over the catheter is required during critical procedures which ablate tissue within the heart. Such procedures are termed xe2x80x9celectrophysiologicalxe2x80x9d therapy and are becoming widespread for treatment of cardiac rhythm disturbances. During these procedures, an operator guides a catheter through a main artery or vein into the interior of the heart which is to be treated. The operator manipulates a mechanism to cause an electrode which is carried on the distal tip of the catheter into direct contact with the tissue area to be treated. Energy is applied from the electrode into the tissue and through an indifferent electrode (in a uni-polar electrode system) or to an adjacent electrode (in a bi-polar electrode system) to ablate the tissue and form a lesion. The irradiation of tissue must be accomplished with great precision as the danger of also damaging other adjacent tissue is always present, especially when the process occurs remotely at the distal end of a relatively long catheter.
One partial solution to this problem has been to xe2x80x9cmapxe2x80x9d the area to be treated prior to a procedure. Cardiac mapping can be used prior to ablation to locate aberrant conductive pathways within the heart. The aberrant conductive pathways are called arrhythmias. Mapping of the heart identifies regions along these pathways, termed xe2x80x9cfocixe2x80x9d, which are then ablated to treat the arrhythmias.
During laser ablation procedures, a catheter serves to deliver a fiber optic wave guide to the target region. Radiation transmitted through the optical fiber essentially vaporizes the targeted tissue to achieve the desired therapeutic goals of the procedure. Complete destruction of target tissue, with the exception of certain narrow and specific cardiac treatments, is generally limited to cardiological applications, e.g., removal of a blockage. In electrophysiological treatments, total destruction of target tissue (ablation) is not necessary, but controlled denaturation of tissue to affect its electrophysiological properties is required.
Within the heart, variations in cardiac tissue characteristics, perhaps as the result of scarring from previous cardiac trauma, can present vastly different tissue that react differently to the laser energy source. For example, absorption characteristics of normal tissue can be much different from tissue that is heavily scarred. In addition, the trabecular nature of the endocardium increases the difficulty because the laser radiation must reach a highly contoured or folded target tissue surface. As a result, temperatures of the tissue surface where the laser energy is incident can be much higher for some tissue than for others. In the treatment of cardiac tissue, the dynamic state of the heart tissue further complicates the situation in that the heart is constantly moving during treatment. Thus, incorporation of fixation means to maintain the position of the distal end of the laser catheter with respect to the target tissue site is often required.
There are drawbacks with many of the currently available catheters and treatments. Oftentimes it is difficult, if not impossible, to maneuver the instrument into small passage ways, such as a ventricle, without damaging the surrounding tissue. Most therapeutic treatments require that the apparatus is in contact with the tissue and with blood and/or other body fluids. Additionally, focusing the ablative energy onto the tissue site to be treated can be problematic, especially when vital organs surround the diseased tissue. Therefore, it would be desirable to focus ablative energy onto a specific treatment area wherein surrounding tissue is not degraded, the energy source is not in direct contact with the tissue and blood and body fluids are not coagulated or destroyed.
The present invention circumvents the problems described above by delivering energy, e.g., laser light or other ablative energy, in an annular pattern without requiring direct contact with an energy source, e.g. a laser (via fiber), with the targeted tissue. This indirect contact with the targeted tissue provides an advantage that damage to surrounding tissues is minimized or eliminated. More specifically, in cardiac therapy, another advantage is that an annular conduction block is created about the pulmonary vein orifice, thereby eliminating aberrant wave conduction.
In one embodiment, the present invention includes an apparatus for inducing phototherapeutic processes in tissue which can include ablation and/or coagulation of the tissue. Typically the optical apparatus is contained within a catheter including a flexible elongate member having a proximal end, a distal end and a longitudinal first lumen extending therebetween. The distal end of the flexible elongate member is open or includes a transparent cap, a centering balloon, or a centering coil. The optical apparatus of the invention can be slidably extended within the first lumen for projecting light through or from the distal end of the flexible member. Alternatively, the optical fiber and other light projecting elements can be fixed in place with the catheter.
The optical apparatus of the invention includes an optical wave guide for projecting an annular pattern of light and a light transmitting optical fiber. Radiation, e.g., infrared, visible or ultraviolet light is propagated through the optical fiber which is in communication with the pattern-forming wave guide. The wave guide/lens is configured to project an annular light pattern such that an annular lesion is formed in tissue. In one embodiment, the annular light pattern expands over distance and is in the form of a ring or a halo. The optical apparatus includes a graded intensity lens (GRIN) or standard refractive optics in addition to the optical wave guide to project the annular light pattern.
In certain embodiments, the optical apparatus of the invention is slidably positioned within the lumen of a catheter proximate to a tissue site. The catheter can include a balloon member fixedly attached to the catheter. Injection of a solution or gas expands the balloon, thereby forcing blood and/or other body fluids from the tissue site. Positioning the optical apparatus permits control over the size of the forwardly projected annular ring to be dynamically changed to accommodate varied pulmonary vein diameters.
The present invention also pertains to methods for forming an annular lesion in a tissue by phototherapeutic processes in tissue which can include ablation and/or coagulation of the tissue. The methods include introduction of an optical apparatus proximate to a tissue site via, for example, a catheter. The optical apparatus includes a pattern-forming optical wave guide that is in communication with a light transmitting optical fiber. Energy is transmitted through the optical fiber, such that radiation propagated through the optical fiber and wave guide projects an annular light pattern, e.g., a circle or a halo. By these methods, an annular lesion can be formed in a targeted tissue. In certain embodiments, the tissue forms a lumen, e.g., vascular, atrial, ventricular, aterial, brachial, or uretral lumen. Preferably the methods include projecting an annular light pattern through a graded intensity lens that is adjacent to the optical wave guide. This additional step forwardly projects the light pattern.
The present invention further pertains to methods for forming annular lesions in cardiac tissue, e.g., trabecular tissue, by phototherapeutic processes which can include ablation and/or coagulation of the tissue. The methods include introduction of an optical apparatus proximate to the cardiac tissue via, for example, a catheter. The optical apparatus includes a pattern-forming optical wave guide in communication with a light transmitting optical fiber. Energy is transmitted through the optical fiber, such that radiation is propagated through the optical fiber, the wave guide and GRIN lens to forwardly project an annular light pattern, e.g., a circle or a halo. In a preferred embodiment, a balloon is inflated against the tissue, thereby forcing blood and/or body fluids away from the tissue targeted for treatment. Light energy is then passed through the optical apparatus onto the targeted tissue such that an annular image is projected onto the site which causes ablation, coagulation or photochemical processes to occur.
The present invention also pertains to methods for treating or preventing atrial arrhythmias by phototherapeutic processes in atrial tissue. These processes can include ablation and/or coagulation of the tissue. The methods include introducing an optical apparatus proximate to atrial tissue via, for example, a catheter. The optical apparatus includes an optical wave guide in communication with a light transmitting optical fiber. Energy is transmitted through the optical fiber, such that radiation is propagated through the optical fiber and the wave guide projects an annular light pattern. The annular light pattern forms an annular lesion in the atrial tissue, thereby treating or preventing atrial arrhythmias.
The methods of the invention can be performed therapeutically or prophylactically. In one embodiment, the treatment method is performed on the atrial wall around the atrial/pulmonary vein juncture or around the pulmonary vein, or within the puhnonary vein. A circular or ring-like section within the pulmonary vein is created by the method of the invention. Formation of one or more circular lesions about the outside or inside diameter of the vein, impedes the conduction of irregular electrical waves to the atrium.